The present invention relates to nanoelectromechanical (NEM) switch systems and transistors. In particular, the present invention relates to NEMSS that can be utilized as traditional electrical components such as, for example, transistors, amplifiers, adjustable diodes, inverters, memory cells, pulse position modulators (PPMs), variable resistors, and switching systems.
As designs for metal-oxide semiconductor field effect transistors (MOSFETs) become more compact and approach the minimum theoretical sizing limitations for a MOSFET, the need for technologies that can produce smaller transistor structures becomes apparent. It is therefore desirable to fabricate a transistor that can be sized smaller than a transistor fabricated at the minimum theoretical size of a MOSFET. By decreasing a transistor's size, the number of transistors that may be placed on an integrated circuit increases. As a result, circuit complexity increases, speed increases, and the circuit's operating power decreases.
Microelectromechanical systems (MEMS) and NEMSS that are structured around nanotubes have been developed. Such systems are described, for example, in commonly assigned copending U.S. patent application Ser. No. 09/885,367 to Pinkerton that was filed on Jun. 20, 2001. Looking at FIG. 11 of this application, a novel power generator that utilizes a nanotube immersed in a working fluid to generate electrical power from the kinetic and thermal characteristics of a working substance is illustrated. As shown by the application, nanotubes can be fabricated at extremely small sizes (e.g., 1 nanometer) and their characteristics (e.g., elasticity and conductivity) may be utilized in many different ways. It is therefore desirable to realize nanotube-based transistors that can be fabricated to have sizing limitations roughly equivalent to the size of a single nanotube.
Sizing limitations are not the only limitations that affect the performance characteristics and utility of a traditional MOSFET. For example, traditional MOSFETs have minimum turn-ON voltages (e.g., 0.7 volts). Thus, miniscule voltage signals (e.g., 0.00001 volts) cannot be utilized to turn on conventional MOSFETs. Numerous applications exist in which there is a need for transistors with small turn-ON voltages. For example, applications in which faint signals, such as thermal or electromagnetic noise signals, need to be recognized would benefit from transistors with extremely low turn-ON. It is therefore desirable to realize a transistor structure with a very low turn-ON voltage.
Additionally, traditional MOSFETs exhibit linear output characteristics. More particularly, traditional MOSFETs may be configured to provide an output (e.g., emitter current) that is continuous and has a linear gain dependent upon an input (e.g., base current). Applications exist in which the need for devices that can convert continuous signals to digital signals is present such as in pulse position modulation. However, traditional pulse position modulators are currently bulky because they require circuits that contain multiple instances of traditional MOSFET transistors. It is therefore desirable to fabricate a single NEM transistor that can function as a pulse position modulator.